Keto enol ether (preparation can be found in J. Org. Chem. 2012, 77, 3846-3858)

vinyl magnesium bromide (0.8 M, Sigma Aldrich)

tetrahydrofuran (ultra low water, J.T. Baker)

In a dry 100 mL round bottom flask containing the 2-benzylidene-tetrahydropyran-3-one (0.307 g, 1.18 mmol) and fitted with a septum was added dry tetrahydrofuran (32 mL) via syringe under nitrogen atmosphere. The mixture was cooled to 0° C by placing the flask on an ice bath. Cold vinyl magnesium bromide (14.75 mL, 11.8 mmol) was added dropwise to the mixture with stirring at 0° C. The reaction slowly warmed to room temperature and was allowed to stirred overnight at rt. After, the reaction was once again placed on an ice bath and cooled to 0° C. The septum was removed and the reaction was quenched by the dropwise addition of ice cold water (5 mL). The mixture was then added to a separatory funnel to which was added an additional 10 mL water. After shaking, the ether layer was set aside and the aqueous layer was extracted with additional ether (2 x 10 mL). The combined ether layers were dried with Na₂SO₄ and then filtered. The solvent was removed under reduced pressure and the syrupy residue was purified by silica gel chromatography using 7:3 hexanes:ethyl acetate as eluent to give the vinyl addition product 0.257 g (88%) as a clear, colorless oil.

R_f 0.48 (7:3 Hex:EtOAc); [α]_D +28.59 (c 0.91, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 7.65 (d, J = 7.5 Hz, 2H), 7.31 (t, J = 7.5 Hz, 2H), 7.16 (t, J = 7.3 Hz, 1H), 6.0 (dd, J = 10.6, 17.4 Hz, 1H), 5.88 (s, 1H), 5.62 (d, J = 17.2 Hz, 1H), 5.48 (d, J = 10.9 Hz, 1H), 4.53 (ddd, J = 3.1, 6.4, 7.7 Hz, 1H), 4.37 (d, J = 7.9 Hz, 1H), 4.32 (dd, J = 3.3, 12.2, 1H), 4.21 (dd, J = 2.9, 12.2, 1H), 3.00 (s, 1H), 1.48 (s, 3H), 1.41 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 151.7, 137.6, 136.0, 128.6, 128.3, 125.9, 120.2, 110.2, 105.3, 77.2, 73.2, 72.5, 64.4, 26.6, 25.0; TOF HRMS (DART) m/z (M+H)⁺ calcd for C₁₇O₄H₂₁ 289.1440, found 289.1414.